@oristarA,
I already mentioned what "fragmentation" means.
Android is a phone operating system provided by Google. Several companies manufacture different kinds of phones that run Android. The problem is that each phone manufacturer customizes their version of Android OS to suit there purposes.
To a regular consumer, any given version of Android say version X will look different on each manufacturer's phone so to the customer's eye, each Android phone looks like it has a completely different OS. The wide array of different user experiences between one phone to the next is described as fragmentation.